In today's world, many vehicles are equipped with systems for facilitating remotely controlled vehicle functions such as passive entry and passive starting (i.e., PEPS) of a host vehicle. When a vehicle is equipped with a PEPS system, a user carries a mobile communication unit which can communicate with a base station located in the vehicle. To conserve use of energy stored in its internal battery, system components may remain in a low power state until an initiating trigger (for example, manipulation of a vehicle door handle) awakens one or more other system components. For example, upon sensing that a door handle has been manipulated, the base station may emit a relatively powerful Low Frequency (LF) electromagnetic field, causing a mobile communication unit that is sufficiently close to the base station to awaken. Once the mobile communication unit is awake, it may use Radio Frequency (RF) transmissions to dispatch a response signal, which may be validated by the base station. If the base station recognizes and approves the identity of the mobile communication unit, (i.e., the base station authenticates the mobile communication unit), the base station may facilitate the performance of a predefined vehicle function, such as actuating a door lock mechanism, causing the door to become unlocked.
Because the amount of energy required by the base station to generate a LF field is significant, many such systems employ a sleep mode and awaken only upon the occurrence of a trigger event. Unfortunately, the use of an initiating trigger causes the sequence of authenticating the mobile communication unit to be performed within an extremely short amount of time so as to avoid the nuisance of experiencing a delay in the vehicle response. Fast-release motors may be employed to perform the actuation functions such as unlocking a door.
Means may be provided for monitoring movements of the mobile communication unit such that, after a period of time in which the mobile communication unit has remained stationary and has not been otherwise activated, the mobile communication unit would be caused to enter the sleep mode. Unfortunately, when the mobile communication unit is in the vehicle, physical movements of the vehicle may be misinterpreted as movements of the mobile communication unit even though the mobile communication unit may be stationary with respect to the vehicle. Under those circumstances, the misinterpreted vehicle movements may prevent the mobile communication unit from entering the sleep mode whenever the vehicle is moving. The present invention attempts to address or ameliorate at least some of the above problems associated with vehicle communication systems.